This invention relates generally to infiltrated matrix drilling products including, but not limited to, matrix drill bits, bi-center bits, core heads, and matrix bodied reamers and stabilizers. More particularly, this invention relates to hard-faced infiltrated matrix drilling products and the methods of hard-facing such items.
FIG. 1 shows a perspective view of an infiltrated matrix drill bit 100 in accordance with the prior art. Referring to FIG. 1, the infiltrated matrix drill bit 100, or drill bit, includes a bit body 110 that is coupled to a shank 115. The shank 115 includes a threaded connection 116 at one end 120. The threaded connection 116 couples to a drill string (not shown) or some other equipment that is coupled to the drill string. The threaded connection 116 is shown to be positioned on the exterior surface of the one end 120. This positioning assumes that the infiltrated matrix drill bit 100 is coupled to a corresponding threaded connection located on the interior surface of a drill string (not shown). However, the threaded connection 116 at the one end 120 is alternatively positioned on the interior surface of the one end 120 if the corresponding threaded connection of the drill string (not shown) is positioned on its exterior surface in other exemplary embodiments. A bore (not shown) is formed longitudinally through the shank 115 and the bit body 110 for communicating drilling fluid from within the drill string to a drill bit face 111 via one or more nozzles 114 during drilling operations.
The bit body 110 includes a plurality of blades 130 extending from the drill bit face 111 of the bit body 110 towards the threaded connection 116. The drill bit face 111 is positioned at one end of the bit body 110 furthest away from the shank 115. The plurality of blades 130 form the cutting surface of the infiltrated matrix drill bit 100. One or more of these plurality of blades 130 are either coupled to the bit body 110 or are integrally formed with the bit body 110. A junk slot 122 is formed between each consecutive blade 130, which allows for cuttings and drilling fluid to return to the surface of the wellbore (not shown) once the drilling fluid is discharged from the nozzles 114. A plurality of cutters 140 are coupled to each of the blades 130 and extend outwardly from the surface of the blades 130 to cut through earth formations when the infiltrated matrix drill bit 100 is rotated during drilling. The cutters 140 and portions of the bit body 110 deform the earth formation by scraping and/or shearing. The cutters 140 and portions of the bit body 110 are subjected to extreme forces and stresses during drilling which causes surface of the cutters 140 and the bit body 110 to wear. Eventually, the surfaces of the cutters 140 and the bit body 110 wear to an extent that the infiltrated matrix drill bit 100 is no longer useful for drilling and is either repaired for subsequent use or is disposed and replaced by another drill bit. Although one embodiment of the infiltrated drill bit has been described, other infiltrated drill bit embodiments known to people having ordinary skill in the art are applicable to exemplary embodiments of the present invention.
FIG. 2 shows a cross-sectional view of a down hole tool casting assembly 200 used in fabricating the infiltrated matrix drill bit 100 (FIG. 1) in accordance with the prior art. Referring to FIG. 2, the down hole tool casting assembly 200 consists of a mold 210, a stalk 220, one or more nozzle displacements 222, a blank 224, a funnel 240, and a binder pot 250. The down hole tool casting assembly 200 is used to fabricate a casting (not shown) of the infiltrated matrix drill bit 100.
According to a typical casting apparatus and method as shown in FIG. 2, the mold 210 is fabricated with a precisely machined interior surface 212, and forms a mold volume 214 located within the interior of the mold 210. The interior surface 212 at least partially surrounds the mold volume 214. The mold 210 is made from sand, hard carbon graphite, or ceramic. The precisely machined interior surface 212 has a shape that is a negative of what will become the facial features of the eventual drill bit face 111 (FIG. 1). The precisely machined interior surface 212 is milled and dressed to form the proper contours of the finished infiltrated matrix drill bit 100 (FIG. 1). Various types of cutters 140 (FIG. 1), known to persons having ordinary skill in the art, can be placed along the locations of the cutting edges of the bit 100 (FIG. 1) and can also be optionally placed along the gauge area of the bit 100 (FIG. 1). These cutters 140 (FIG. 1) can be placed during the bit fabrication process within the mold 210 or after the bit 100 (FIG. 1) has been fabricated via brazing or other methods known to people having ordinary skill in the art.
Once the mold 210 is fabricated, displacements are placed at least partially within the mold volume 214. The displacements are typically fabricated from clay, sand, graphite, or ceramic. These displacements consist of the center stalk 220 and the at least one nozzle displacement 222. The center stalk 220 is positioned substantially within the center of the mold 210 and suspended a desired distance from the bottom of the mold's interior surface 212. The nozzle displacements 222 are positioned within the mold 210 and extend from the center stalk 220 to the bottom of the mold's interior surface 212, which is where the nozzle 114 (FIG. 1) is formed. The center stalk 220 and the nozzle displacements 222 are later removed from the eventual drill bit casting so that drilling fluid can flow though the center of the finished infiltrated matrix drill bit 100 (FIG. 1) during the drill bit's operation.
The blank 224 is a cylindrical steel casting mandrel that is centrally suspended at least partially within the mold 210 and around the center stalk 220. A tooling (not shown), which is known to people having ordinary skill in the art, is used to suspend the blank 224 within the mold 210. The blank 224 is hanged on the tooling and the tooling is lowered so that the blank 224 is positioned a predetermined distance down into the mold 210 and aligned appropriately therein as desired. An upper portion of the blank 224 forms the shank 115 (FIG. 1) after completion of the fabrication process.
Once the displacements 220, 222 and the blank 224 have been properly positioned within the mold 210, tungsten carbide powder 230 is loaded into the mold 210 so that it fills a portion of the mold volume 214 that includes an area around the lower portion of the blank 224, between the inner surfaces of the blank 224 and the outer surfaces of the center stalk 220, and between the nozzle displacements 222. Shoulder powder 234 is loaded on top of the tungsten carbide powder 230 in an area located at both the area outside of the blank 224 and the area between the blank 224 and the center stalk 220. The shoulder powder 234 can be made of tungsten powder. This shoulder powder 234 acts to blend the casting to the steel blank 224 during fabrication and is machinable. Once the tungsten carbide powder 230 and the shoulder powder 234 are loaded into the mold 210, the mold 210 is typically vibrated to improve the compaction of the tungsten carbide powder 230 and the shoulder powder 234. Although the mold 210 is vibrated after the tungsten carbide powder 230 and the shoulder powder 234 are loaded into the mold 210, the vibration of the mold 210 can be done as an intermediate step before the shoulder powder 234 is loaded on top of the tungsten carbide powder 230. Additionally, the vibration of the mold 210 can be done as an intermediate step before the shoulder powder 234 is loaded on top of the tungsten carbide powder 230 and after the shoulder powder 234 is loaded on top of the tungsten carbide powder 230.
The funnel 240 is a graphite cylinder that forms a funnel volume 244 therein. The funnel 240 is coupled to the top portion of the mold 210. A recess 242 is formed at the interior edge of the bottom portion of the funnel 240, which facilitates the funnel 240 coupling to the upper portion of the mold 210. Although one example has been provided for coupling the funnel 240 to the mold 210, other methods known to people having ordinary skill in the art can be used. Typically, the inside diameter of the mold 210 is similar to the inside diameter of the funnel 240 once the funnel 240 and the mold 210 are coupled together.
The binder pot 250 is a cylinder having a base 256 with an opening 258 located at the base 256, which extends through the base 256. The binder pot 250 also forms a binder pot volume 254 therein for holding a binder material 260. The binder pot 250 is coupled to the top portion of the funnel 240 via a recess 252 that is formed at the exterior edge of the bottom portion of the binder pot 250. This recess 252 facilitates the binder pot 250 coupling to the upper portion of the funnel 240. Although one example has been provided for coupling the binder pot 250 to the funnel 240, other methods known to people having ordinary skill in the art can be used. Once the down hole tool casting assembly 200 has been assembled, a predetermined amount of binder material 260, which is ascertainable by people having ordinary skill in the art, is loaded into the binder pot volume 254. The typical binder material 260 is a copper or copper alloy, but can be a different metal or metal alloy, such a nickel or nickel alloy.
The down hole tool casting assembly 200 is placed within a furnace (not shown). The binder material 260 melts and flows into the tungsten carbide powder 230 through the opening 258 of the binder pot 250. In the furnace, the molten binder material 260 infiltrates the tungsten carbide powder 230. During this process, a substantial amount of binder material 260 is used so that it also fills at least a substantial portion of the funnel volume 244 located above the shoulder powder 234. This excess binder material 260 in the funnel volume 244 supplies a downward force on the tungsten carbide powder 230 and the shoulder powder 234. Once the binder material 260 completely infiltrates the tungsten carbide powder 230, the down hole tool casting assembly 200 is pulled from the furnace and is controllably cooled. The mold 210 is broken away from the casting. The casting then undergoes finishing steps which are known to people having ordinary skill in the art, including the addition of the threaded connection 116 (FIG. 1) coupled to the top portion of the blank 224 and the removal of the binder material 260 that filled at least a substantial portion of the funnel volume 244. Although one method and apparatus has been described for fabricating the infiltrated matrix drill bit 100, other methods and/or apparatuses can be used for fabricating the infiltrated matrix drill bit 100 in other exemplary embodiments. Additionally, although exemplary materials have been mentioned for forming the components above, other suitable materials can be used. Further, although the binder material 260 melts and then is poured into the tungsten carbide powder 230, the binder material 260 can be either mixed with the tungsten carbide powder 230 or disposed above the tungsten carbide powder 230 prior to being melted.
Since drill bits are subjected to extreme forces and stresses during drilling which cause wear, manufacturers and/or users of drill bits and other downhole tools have attempted to reduce this wear by applying a hardfacing material directly on at least portions of the surface of the drill bit. The hardfacing material typically includes a first phase that exhibits relatively high hardness and a second phase that exhibits relatively high fracture toughness. The first phase is formed from tungsten carbide; however, other suitable materials can be used including, but not limited to, titanium carbide, tantalum carbide, titanium diboride, chromium carbides, titanium nitride, aluminum oxide, aluminum nitride, and silicon carbide. The second phase is a metal matrix material formed from cobalt or cobalt-based alloys; however, other suitable materials can be used including, but not limited to, iron-based alloys, nickel-based alloys, iron- and nickel-based alloys, cobalt- and nickel-based alloys, iron- and cobalt-based alloys, aluminum-based alloys, copper-based alloys, magnesium-based alloys, and titanium-based alloys. These hardfacing materials are typically brought to a high temperature so that the matrix material melts and bonds to the surface of the drill bit. However, these hardfacing materials do not successfully bond directly to the surface of the infiltrated matrix drill bit 100 because of the presence of the binder material 260 within the infiltrated matrix drill bit 100. Therefore, manufacturers and/or users of drill bits applied the hardfacing material directly onto the surface of a sintered matrix drill bit (not shown), which does not include the binder material 260 that is present within the infiltrated matrix drill bit 100, as described above. A sintered matrix drill bit is fabricated differently than the infiltrated matrix drill bit 100 and is known to people having ordinary skill in the art.